1. Field of the Invention
This invention relates to a projection optical film feeding apparatus and an overhead projector provided with such apparatus, and particularly to an original film feeding apparatus for setting original film at a predetermined location on the platen glass of an OHP apparatus for projecting, for example, original film (OHP film) and an overhead projector equipped with the same.
2. Related Background Art
Generally, in an announcement, a lecture or the like utilizing an OHP apparatus, the speaker writes image information on transparent sheet-like OHP film to thereby prepare original film (hereinafter referred to as the "sheet"), sets this sheet on the platen glass of the OHP apparatus, applies light thereto from below and enlargedly projects the original image onto a front screen. The speaker then stands by the screen and gives an explanation to the audience while pointing at the image enlarged on the screen by the use of a pointing rod or the like. When the explanation of a sheet is ended, the speaker removes this sheet from the platen glass and places a new sheet necessary for the next explanation onto the platen glass. By repeating the removal of an explained sheet and the placement of a new sheet in this manner, the speaker interchanges the sheets prepared and arranged in advance in the order of announcement one after another on the platen glass and makes the explanation of the sheets in succession on the screen.
According to the above-described example of the prior art, however, the speaker approaches the OHP apparatus and talks while interchanging the sheets on the platen glass one after another, and this has led to the following disadvantages:
(1) The OHP apparatus and the screen are usually installed with a distance therebetween and accordingly, during the interchange of the sheets, the speaker needs to move from the screen to the OHP apparatus, and this is inefficient. Therefore, in some cases, the speaker is in constant attendance upon the screen and posts a person for the interchange of the sheets, and the person interchanges the sheets in response to the speaker's sign. PA1 (2) As when answering questions after the announcement, the speaker takes much time to find out a necessary sheet or sheets from among the announced sheets placed in disorder and cannot effectively make the most of the limited announcement time. PA1 (3) When a sheet is to be placed onto the platen glass, the sheet is curled at the four corners thereof and the four corners of the image projected on the screen becomes distorted. Also, the interchange of the sheets is done hastily in a dark place and therefore, the top and bottom or the front and back of a sheet are apt to be mistaken for each other.